Torque Monster !

[mgoblue9798]

Yes but, from memory, the reduction is about the same as simply downshifting the main trans. About 33%; which turns a 5.56 into a 7.39, and rpm will jump from 2400 to 3200. Whereas a downshift from overdrive to "Drive "is 3480. I don't see a 2-speed particularly useful in this case.

But I do see it, if you do NOT have an overdrive trans, and worked the rear backwards like an overdrive.
Now for comparison, 4.56 x.69od in the A518, =3.15 for 70=2400
To equal that with a two-speed operating in reverse mode. would require
3.15 x1.33=4.20s in the back.
But say you found one with 3.91s.....
then, the planetary speed will be 3.91 x1.33=5.20 Now you could be in low range for take-off, hitting 4000 in drive at about 65mph, then into high range the Rs would drop to 4000 x 1/1.33=3000@ 65mph. Then into lock-up the Rs fall to 2550, still at 65; and 70 would then be 2750. Still in 3.91 Hi-range in the diff.
For comparison, 1/1.33= .75 or 75% That is a nice progression for the A727, which would be
2.45-1.45-1.00-.75"overdrive" ; with splits of
.59-.69-.75 just what your rig needs. I like it.
Looking at it in roadgears, with a 3.91 C&P starting out in 1.33 low-range, I get
12.74-7.54-5.20-3.91 and loc-up. And 70=2750
Compare that to the A518 and 4.56s;
11.17-6.61-4.56-3.15 and loc-up. And 70=2400
In "fourth gear" the 2-speed 3.91 is 24% better than A518.
With 400 ftlbs on tap, this amounts to an extra 100 ftlbs available for climbing/etc without downshifting... which is a good thing, cuz those 2-speed units do not like to be downshifted at speed. Once you get to cruise-speed, you want to leave the two-speed in high range.
But as you can see, even with 3.91s your starter gear is 14% better for about a half-gear jump off the line.

In both cases, the TC will add it's own multiplier, varying perhaps from 1.8 to 1.1 ,with load and rpm.

I don't see a bad side to this idea.
You don't need an A518 nor adapters. Theoretically speaking, if you could find smaller than 3.91s for the back, you wouldn't need a loc-up either, But IDK if that is possible nor even desireable.
But then, you wouldn't need the 413 either, a stout 360........ like mine lol, would do the trick, you might just want to shift it a lil higher than 4000 and wait until 70 to hit Hi-Range.
Oh I can hear that Thermoquad-360 screaming thru the dual 3inchers already, lol.
360s can make 400 tq as well, they just can't give it to you from 2000 to 4000 rpm lol. But with a progressive shifting combo like the 2-speed delivers, it doesn't need to.
But hey, I know you got your sights set on the 413, and I can certainly see the attraction in cruising at 2400, with the engine sitting right there beside you. But to do that with a 2-speed would require a rear C&P of 3.36s, AND a loc-up besides.....if I am right about the 33% planetary ratio increase, going from memory, lol. (I used to build those for a living,back in the 80s)

More spitballing;
The more I think about this, Especially that short progressive shift out of Lo-range, the more I think how a Hi-pressure 360 could easily pull that with a a hi-stall/loc-up, and a short-period cam, and with only 4" pistons, and a long stroke(relatively speaking), Fuel Economy is a shoo-in. Ima thinking up to a 218/223 cam, alloy heads and 185/190psi minimum cranking cylinder pressure.
But hey, now the A518 bolts on....................
Are you thinking what I'm thinking?
Heck-ya. Run both the A518 AND the 2-speed. Say Hello to 70= 2020 in od on the flat close to sealevel, but 2920 at altitude in Drive. And getaload of the take-off power in low range! with 4.10s now, your road gears could be
13.36-7.91-5.45-4.10-2.83, lo-range in red, hi-range in blue.
Count them; 5 speeds not including loc-up.
And nice progressive splits of .59-.69-.75-.69od
Yeah, no; the thermoquad on the 360, IDK if it can pull 70mph in 2.83rear gear, on the teensey primaries,lol. But if it did! now yur all set up, for mpgs.
BTW,
13.36 as above, with 33" tires is the same as;
10.73 with 26.5s, and 4.05s.,
With the TC adding it's multiplier and say a 2800 stall this would make a killer take-off in a 4000 pound car....... Yeah OK I get that your Travco will be a tad heavier than 4000, but you are not likely to ever floor your 413 from a standing stop either.
Ok now, suppose you did floor your 413, and it exploded into 4.56s at all 400 ftlbs. That maths out to 4469 ftlbs thru 2.45 first gear, into the rear axles.
But the 360 into 4.10s x1.33 will need only 335 ftlbs (84%) to match it.
Going back to the 100hp theoretical chassis requirement to cruise at 70mph. At 2020 the 360 would need 260 ftlbs to cruise on the flat. Your 413 at 2400 requires a lil less, at 219. But the 360 is not working all that much harder. And, taking it out of loc-up, might get you say 2376 rpm and now the requirement is 221 ftlbs...... lol.
I love this;
13.36-7.91-5.45-4.10-2.83, lo-range in red, hi-range in blue.
Count them; 5 speeds not including loc-up.
And nice progressive splits of .59-.69-.75-.69od
What do I mean without lock up?
Well the TC adds torque to every gear, depending on the torque going into it from the crank, and the resistance of the chassis to accelerating.
The ratio varies continuouslt between a possible hi of 1.8 to a possible low of 1.1. The multiplier is greatest at zero mph and least when cruising.
So then on the start-line, this 13.36 could be as high as 24:1 !! but as soon as the vehicle starts to move, this multiplier begins to diminish.
Lets say in first gear it averages 1.4, and let's say in second it averages 1.3 and in drive under load it averages 1.2, and when you put it into hi-range, 1.1
Ok your new ratios, which you will be seeing on the tach, reflect this
18.70-10.28-8.63-4.51/4.10locked-up, and 3.11/2.83locked up. Count them; I get 6 or 7,lol, ratios, depending on when you use loc-up. Good stuff.
Fun with math.

An RV type engine is begging for a beer barrel type intake manifold. One thing that would concern me would be piston crown thickness. I'll have to do some measuring. Maybe forged pistons with ceramic coated tops could live?

Another thought is I have read that some RV transmissions come with a lower 2.74 1.54 gear set. Maybe mine has them and can be used in the 518. If it doesn't they used to sell the gear sets a/m. Would make for better gear splits with 1st, 1stod, 2nd, 2od etc.

Serpentine set up is a plus as well. Wire up an OBD2 to run the thing with a tuner. Self tuning for elevation changes.

I have to get this thing home and see exactly what I have to start with.

 

[mbaird]

Magnum based 408 with abeer barrel FI
and headers thru 3" dual exhaust .

The first gear ratio really doesn't matter unless you are towing a big trailer or going for a low 60 ft time .

 

[mgoblue9798]

Magnum based 408 with abeer barrel FI
and headers thru 3" dual exhaust .

The first gear ratio really doesn't matter unless you are towing a big trailer or going for a low 60 ft time .

I am starting to consider this. I already have a 360 roller block, forged pistons, forged scat crank, scat H beams, 214 224 @.050 about 550 lift roller comp cam, and magnum edelbrocks sitting on the shelf.

I will be towing a trailer with my dakota, and a 14ft aluminum jon boat with outboard. Or modify the trans in the dakota so it can be flat towed.

 

[mgoblue9798]

I will be towing a trailer with my dakota, and a 14ft aluminum jon boat with outboard. Or modify the trans in the dakota so it can be flat towed.

I am starting to consider this. I already have a 360 roller block, forged pistons, forged scat crank, scat H beams, 214 224 @.050 about 550 lift roller comp cam, and magnum edelbrocks sitting on the shelf.

 

[mbaird]

Well there you go . Might want a milder cam though .
Run some aluminum heads for heat dissapation and quench , coat the piston tops ,ex valves and chambers for heat.
You should be able to generate 250 ft/lbs+ @ 2200 rpm and 400+ around 3800 .

 

[mgoblue9798]

Well there you go . Might want a milder cam though .
Run some aluminum heads for heat dissapation and quench , coat the piston tops ,ex valves and chambers for heat.
You should be able to generate 250 ft/lbs+ @ 2200 rpm and 400+ around 3800 .

Those numbers are a 5.9 with headers and a cam. Stroker should do a hell of a lot better than that or something is wrong.

 

[AJ/FormS]

The 413 can pull the A500 ratios with ease. But I would hesitate to use them with a small block.The ratios are
2.74-1.54-1.00 w/splits of .562-.649-.69od w/ the A500 ;as compared to
2.45-1.45-1.00 w/splits of .592-.690-.69od w/ the A518.
So shifting at 4000 say, the rpm drops are to; 2248 /2596 with the A500, versus 2368/ 2760 with the A518
But if using the 360 and shifting at 5000, the drops will be to; 2810/3245 with the A500, versus 2960/3450 with the A518
As you can see, there is not a whole big bunch of difference

 

[AJ/FormS]

Alloy heads are a great idea, but since they pull so much heat out of the chambers, you need to run more pressure just to break even on power. But they are certainly up to the task. I run mine at 185psi and 207*F with no problems on 87E10.
Here is a Hughes Engines 360 copy to mine, but with iron heads; and accompanying article.
#11---360 Dyno Test (Feb 2000)

 

[mgoblue9798]

Alloy heads are a great idea, but since they pull so much heat out of the chambers, you need to run more pressure just to break even on power. But they are certainly up to the task. I run mine at 185psi and 207*F with no problems on 87E10.
Here is a Hughes Engines 360 copy to mine, but with iron heads; and accompanying article.
#11---360 Dyno Test (Feb 2000)View attachment 1715683930

I have read a couple articles claiming that aluminum heads needing higher compression than cast iron to maintain similar power levels is not true. Interesting article from car craft: Comparing Aluminum And Iron Cylinder Heads - Car Craft Magazine

 

[AJ/FormS]

Uncle Tony, on the same show, within hours of each other, dynoed a 440 with iron then alloy, and lost power with the alloys. As I recall it was more than 20hp, on a 500hp build. To be fair, the alloys picked up a few ftlbs in the midrange.
On a street SBM that is about one cam size or 5/6psi or more than .5 point of compression.
But again, these are WOT numbers and have nothing to do with your build. The only reason you would have to rev past 4000, is to get a lil higher rpm on the next in-shift.
No, in your combo;
You want Max Running Pressure at cruise rpm. But you can't have it cuz then the engine will detonate the skirts off the pistons, or worse, at WOT. So second best is to run as much cranking-pressure as you dare to, for cruise pressure,and still remain without detonation under full-load/full power.
You can probably do that with 160/165psi in iron on 91 gas. Or with alloys,maybe 185psi on 87E10, 190 on 89, or 195 on 91octane gas. All designs with tight-Q.
That's a 30 psi difference, or 18% increase in pressure, on same grade gas.
I have no idea how that will affect the power curve, but I do know that my engine (180psi/alloy) is way overkill for the mere 3650 pounds it has to haul.
And, the 360 with KB107s practically falls together at the right pressure with closed-chamber alloys.
Now, if it was me, I would run even more pressure, but with meth or water-injection as may be required under power. I was fully prepared to go that way with my build in 1999, because no one knew anything back then, or was certainly not talking about it. But my first combo proved right away that I was ok without it.

 

[mgoblue9798]

Uncle Tony, on the same show, within hours of each other, dynoed a 440 with iron then alloy, and lost power with the alloys. As I recall it was more than 20hp, on a 500hp build. To be fair, the alloys picked up a few ftlbs in the midrange.
On a street SBM that is about one cam size or 5/6psi or more than .5 point of compression.
But again, these are WOT numbers and have nothing to do with your build. The only reason you would have to rev past 4000, is to get a lil higher rpm on the next in-shift.
No, in your combo;
You want Max Running Pressure at cruise rpm. But you can't have it cuz then the engine will detonate the skirts off the pistons, or worse, at WOT. So second best is to run as much cranking-pressure as you dare to, for cruise pressure,and still remain without detonation under full-load/full power.
You can probably do that with 160/165psi in iron on 91 gas. Or with alloys,maybe 185psi on 87E10, 190 on 89, or 195 on 91octane gas. All designs with tight-Q.
That's a 30 psi difference, or 18% increase in pressure, on same grade gas.
I have no idea how that will affect the power curve, but I do know that my engine (180psi/alloy) is way overkill for the mere 3650 pounds it has to haul.
And, the 360 with KB107s practically falls together at the right pressure with closed-chamber alloys.
Now, if it was me, I would run even more pressure, but with meth or water-injection as may be required under power. I was fully prepared to go that way with my build in 1999, because no one knew anything back then, or was certainly not talking about it. But my first combo proved right away that I was ok without it.

I'll have to check out the UT dynoes. I wonder if they were same/same as far as port size, chamber size, flow, valve size ,etc. The thing I found interesting about the CC article as both sets of heads were Darts that were damn near identical in every way.

Lets use my high top conversion van as an example for a minute. When I put the fresh rebuild in, it was 165psi with stock 5.9 pistons, .028 head gasket, Hughes prepped EQ heads as cast chamber size with 1.92 intakes, and a Hughes 0814 roller cam. That was with only the one plug pulled for the gauge, not all 8.

It is a sail in the wind as the motorhome is. I have pulled a 2500lb trailer with a 3700lb car loaded on it and not once has it had audible knock or any signs of detonation (plugs were clean).

With 3.55's 46RE, 30.6" tire at 85mph it is still pulling like a freight train with almost half a pedal to go to full throttle, and turning about 2700 rpm.

Based on that engine I don't know why it would not be possible to run an even higher cylinder pressure with good quench, especially with aluminum heads, a good cold air source, and headers. One advantage I will have is the RV has the main gas tank along with a reserve tank. I could keep high test or even E87 in it in case I got into trouble. I would like to run the cheap stuff as much as possible as I do in my van.

 

[AJ/FormS]

Lets use my high top conversion van as an example for a minute. When I put the fresh rebuild in, it was 165psi with stock 5.9 pistons, .028 head gasket, Hughes prepped EQ heads as cast chamber size with 1.92 intakes, and a Hughes 0814 roller cam. That was with only the one plug pulled for the gauge, not all 8.

That's a really nice combo.
With 3.55s and 30.6 tires, that is the equivalent of running 2.98s with 26.5s, to put it into perspective for me. For you to laud the 5.9 at 2700, is proof of that engine's capabilities.
I'm assuming that 5.9 is still equipped with the factory EFI system, which has timing control, a knock sensor, and that wicked keg intake, which is basically a reshaped tunnel-ram.
As already mentioned, that's a great way to go. That 0814 cam is also a good pick for torque.
The only way you can run more pressure with that 5.9 which is already at or near the pressure limit, is to run in conjunction, either a detonation suppressant like water/meth injection; or to run alloy heads. But in the Travco case, IDK if that is such a great idea.
Firstly, to get 165psi with iron at sea level points to 9.5Scr and an Ica of 56*, with a resultant PV predicted to be 148, a very nice number for a streeter.
To beat this with alloy,is gonna take about 10.5Scr Which points to a total chamber size of 77.6cc, and you can't get away with that .028 gasket anymore unless you can figure out how to keep the pressure from blowing the Fire-ring into the valley. So you are "stuck" with the FelPro .039s (8.8cc). You are gonna have to mill the decks to get the pistons up to at least zero-deck. Mine are at .003 to .007, above deck. This means everything has to be machined just about perfect. My stuff has been to three different machine shops, each saying they could do better than the last one. Well not one of them could. The stack up gets critical when you want to run .030 or less Q. The block could be off a tad. the rods could end up resized to 8 different lengths, the crank could be off a hair, and if you line-hone the block, all bets are off. It took me more than a full morning to get my deck-heights to the range they are in. Only the KB107s were the same to 3 decimal points. But you know; they say .040 is as close as you need to get. My tightest is .032, by the math after measurement. So at zero-deck, the KB107s are listed at 5cc.The total now is 8.8+5=13.3, leaving 63.8 for the heads. easy peasy; so the compression and Q problems are solved, and 10.5 at stock 4.0x3.58 is done.
Here's the problem as I see it;
With that 0814 cam the Ica is sorta predicted to be 56*, and if that is true, then the pressure is predicted to be 187psi at sealevel. I say sorta because Hughes, as is their policy, does not publish the advertised duration specs; so I guessed. I guessed that the 0814 cam is 256/264/110 advertised.
Now there is nothing wrong with 187 psi with alloys either, but in this case it comes with a P/V index of 168; read about PV here;
V/P Index Calculation
A PV of 168 is flipping huge. That is what my engine runs, and she's a parts breaker in my 3650 pound Barracuda, with a manual trans. It has at one time or another, broken every member behind it, and is particularly hard on clutch discs. It broke;
2 of A833 overdrives
a 5.13/5.38 Crown gear, Can't recall exactly which
a 3.91 crown gear.
a 7260 u-joint was no match
the 7290 held up better
and the 1350 finally solved it.
She can blow up a factory 340 disc in just hours.
On the street! mind you, every one on the street. with those BFG/Cooper 295/50-15s yet, that everyone rightly calls crappy,lol.
For comparison, the 1968 Chrysler 440Magnum maths to a VP of 150.
Now if you read the supplied PV link, you already know that VP is a measure of Low-Rpm Performance, the purpose of which is to be able to bring that performance comparison into a useful apples to apples relationship. Like saying the 440M has 150Vp, and it will compare well to a 5.9M with 148VP, like yours. And this has nothing to do with Horsepower; but is instead trying to tell you something about the low-rpm performance. Obviously if you hung a 3500TC on the back of that 5.9, VP would be meaningless.

So the question then is:
is 168VP a good fit for your Travco? Or better asked is this;
is it a better fit than the 148VP of the 165psi Magnum you already have?
Sometimes more is not the best answer.
If you run a 2-speed rear as previously talked about, you will never have to floor this Magnum during the run to 70 mph. You can, but you don't have to.
So hang on a sec; what good reason can you then give, to justify the cost of replacing perfectly good iron EQ heads, with alloy anything? See what I mean.

OK I'll answer that;
Because now you can pitch that wiener 0814 cam, sacrifice some of that excessive bottom-end VP, and pick up some serious power up top. That's why.
But is that a good thing?
Heck ya for a 3650 pound streeter like mine, which is why I did it,lol. But for your Travco? Not hardly, because that power comes at or near 5000 rpm, which, with the current combo and a 727 gearing, will come exactly once/maybe twice, on the way to 70mph, namely at the top of First gear. and then; even with 4.56s out back, 70 in Second gear with 33s is 4700/no slip; perhaps 5200 at 10% slip.
Will it be fun?
Heck ya.
But there is another reason not to go to a bigger cam; namely efficiency. As you go to ever bigger cams, you are pushing the operating rpm up. The useful, power-making rpm. But it comes at the expense of eating up the bottom end of that useful operating rpm, each bigger cam size (about 7*) will move the power about 200rpm higher at the top, while simultaneously taking about 100rpm off the bottom, in terms of driveability. And so begins the march into gas-hog territory. If the march ends up in your chosen cruise rpm, well then, you can kiss fuel-economy good bye.
Now in your case a cruise rpm of 2400 is still fairly high, and I think there is room for nearly two more cam sizes, from the 0814 before getting into trouble with the alloy heads. But two more sizes will plummet your PV back to about what you have now.
So, all in all, if it doesn't mess up your fuel-economy, it could be a good deal.
But, then comes the price tag. Is it worth it to you to purchase the alloy heads and the new cam kit, which may need all new valve operating gear; while simultaneously pumping up the Scr to get 30/40 horsepower at 5000 rpm, which you will only go to when you need to satisfy your own personal need to hear the engine screaming? I mean that's exactly why I did it,lol.
And then, after all that, unless you have a computer controlled timing map, You still will have major hurdles to solve, to get adequate Cruise-Timing.

Once again, jus spitballing ideas around.

 

[mgoblue9798]

That's a really nice combo.
With 3.55s and 30.6 tires, that is the equivalent of running 2.98s with 26.5s, to put it into perspective for me. For you to laud the 5.9 at 2700, is proof of that engine's capabilities.
I'm assuming that 5.9 is still equipped with the factory EFI system, which has timing control, a knock sensor, and that wicked keg intake, which is basically a reshaped tunnel-ram.
As already mentioned, that's a great way to go. That 0814 cam is also a good pick for torque.
The only way you can run more pressure with that 5.9 which is already at or near the pressure limit, is to run in conjunction, either a detonation suppressant like water/meth injection; or to run alloy heads. But in the Travco case, IDK if that is such a great idea.
Firstly, to get 165psi with iron at sea level points to 9.5Scr and an Ica of 56*, with a resultant PV predicted to be 148, a very nice number for a streeter.
To beat this with alloy,is gonna take about 10.5Scr Which points to a total chamber size of 77.6cc, and you can't get away with that .028 gasket anymore unless you can figure out how to keep the pressure from blowing the Fire-ring into the valley. So you are "stuck" with the FelPro .039s (8.8cc). You are gonna have to mill the decks to get the pistons up to at least zero-deck. Mine are at .003 to .007, above deck. This means everything has to be machined just about perfect. My stuff has been to three different machine shops, each saying they could do better than the last one. Well not one of them could. The stack up gets critical when you want to run .030 or less Q. The block could be off a tad. the rods could end up resized to 8 different lengths, the crank could be off a hair, and if you line-hone the block, all bets are off. It took me more than a full morning to get my deck-heights to the range they are in. Only the KB107s were the same to 3 decimal points. But you know; they say .040 is as close as you need to get. My tightest is .032, by the math after measurement. So at zero-deck, the KB107s are listed at 5cc.The total now is 8.8+5=13.3, leaving 63.8 for the heads. easy peasy; so the compression and Q problems are solved, and 10.5 at stock 4.0x3.58 is done.
Here's the problem as I see it;
With that 0814 cam the Ica is sorta predicted to be 56*, and if that is true, then the pressure is predicted to be 187psi at sealevel. I say sorta because Hughes, as is their policy, does not publish the advertised duration specs; so I guessed. I guessed that the 0814 cam is 256/264/110 advertised.
Now there is nothing wrong with 187 psi with alloys either, but in this case it comes with a P/V index of 168; read about PV here;
V/P Index Calculation
A PV of 168 is flipping huge. That is what my engine runs, and she's a parts breaker in my 3650 pound Barracuda, with a manual trans. It has at one time or another, broken every member behind it, and is particularly hard on clutch discs. It broke;
2 of A833 overdrives
a 5.13/5.38 Crown gear, Can't recall exactly which
a 3.91 crown gear.
a 7260 u-joint was no match
the 7290 held up better
and the 1350 finally solved it.
She can blow up a factory 340 disc in just hours.
On the street! mind you, every one on the street. with those BFG/Cooper 295/50-15s yet, that everyone rightly calls crappy,lol.
For comparison, the 1968 Chrysler 440Magnum maths to a VP of 150.
Now if you read the supplied PV link, you already know that VP is a measure of Low-Rpm Performance, the purpose of which is to be able to bring that performance comparison into a useful apples to apples relationship. Like saying the 440M has 150Vp, and it will compare well to a 5.9M with 148VP, like yours. And this has nothing to do with Horsepower; but is instead trying to tell you something about the low-rpm performance. Obviously if you hung a 3500TC on the back of that 5.9, VP would be meaningless.

So the question then is:
is 168VP a good fit for your Travco? Or better asked is this;
is it a better fit than the 148VP of the 165psi Magnum you already have?
Sometimes more is not the best answer.
If you run a 2-speed rear as previously talked about, you will never have to floor this Magnum during the run to 70 mph. You can, but you don't have to.
So hang on a sec; what good reason can you then give, to justify the cost of replacing perfectly good iron EQ heads, with alloy anything? See what I mean.

OK I'll answer that;
Because now you can pitch that wiener 0814 cam, sacrifice some of that excessive bottom-end VP, and pick up some serious power up top. That's why.
But is that a good thing?
Heck ya for a 3650 pound streeter like mine, which is why I did it,lol. But for your Travco? Not hardly, because that power comes at or near 5000 rpm, which, with the current combo and a 727 gearing, will come exactly once/maybe twice, on the way to 70mph, namely at the top of First gear. and then; even with 4.56s out back, 70 in Second gear with 33s is 4700/no slip; perhaps 5200 at 10% slip.
Will it be fun?
Heck ya.
But there is another reason not to go to a bigger cam; namely efficiency. As you go to ever bigger cams, you are pushing the operating rpm up. The useful, power-making rpm. But it comes at the expense of eating up the bottom end of that useful operating rpm, each bigger cam size (about 7*) will move the power about 200rpm higher at the top, while simultaneously taking about 100rpm off the bottom, in terms of driveability. And so begins the march into gas-hog territory. If the march ends up in your chosen cruise rpm, well then, you can kiss fuel-economy good bye.
Now in your case a cruise rpm of 2400 is still fairly high, and I think there is room for nearly two more cam sizes, from the 0814 before getting into trouble with the alloy heads. But two more sizes will plummet your PV back to about what you have now.
So, all in all, if it doesn't mess up your fuel-economy, it could be a good deal.
But, then comes the price tag. Is it worth it to you to purchase the alloy heads and the new cam kit, which may need all new valve operating gear; while simultaneously pumping up the Scr to get 30/40 horsepower at 5000 rpm, which you will only go to when you need to satisfy your own personal need to hear the engine screaming? I mean that's exactly why I did it,lol.
And then, after all that, unless you have a computer controlled timing map, You still will have major hurdles to solve, to get adequate Cruise-Timing.

Once again, jus spitballing ideas around.

The engine I have running the Hughes cam is in my high top conversion van. It stays in it.

The motorhome engine will be a fresh build.

I have a couple 440's including a short block six pack rod and piston combo that sit just shy of zero deck (.010), a free core 413-3 that I just have to pick up, several 360 roller magnum blocks and good oem stock stroke cranks. I have 4 good sets of magnum style heads sitting on the shelf collecting dust. Edlebrock aluminum magnum heads, RHS X heads, and two sets of EQs. Steel heads are 1.92 with about 230 cfm flow, Eddys are 2.02 and 250 or so cfm according to what I have read not measured.

I also have an hughes edlebrock air gap EFI manifold, but think one of Marty's modified keggers at utawesomeperformance.com might be a better choice for the RV. I have two stroker 408/5.9 crank/rod/pistons combos. I also have a comp roller cam with 214/224 .050 and about .550 lift.

I have a set of RV 413 headers, and a set of mopar performance mid length 5.9 headers. All of these parts are sitting unassembled in my shop available.

If using the 5.9 I can wire up the oem obd 2 computer to run the engine and get a custom tune, while running a 46 RH manually to control gear splits. I have both lock up and non lockup trans cores to build.

I have no problems using any combo of these parts or acquiring more stuff to build the ideal motor for this application.

Given the 518, 4.56 or 4.88 gear and a tire height of somewhere 32-34 inches, what would you build as the ideal combo that is the best combination of torque and efficiency, assuming staying with the one speed rear?

 

[AJ/FormS]

Well you sly dog you! What a great parts store house!
Do you have any clue as to the actual scale weight of the Travco?, not GVW
Do you know what rear gears are currently in it?
What does your hi-top scale at?, the one with the peppy 5.9. And what gears are in it?

I cannot speak to BigBlocks, never having had one.

Hit refresh as I'm adding as I go, cuz my computer has a tendency to freeze, and when it does, I loose the drafts.

OOPs. I see

With 3.55's 46RE, 30.6" tire at 85mph it is still pulling like a freight train with almost half a pedal to go to full throttle, and turning about 2700 rpm.

So let's correct that to 33s and I get the 3.55s =3.29s, which represents a loss of performance of 7.3%, so the Travco, to remain on par with the same engine, would need 3.55s plus 7.3% = 3.81s
and the proof is;
with 3.55s and 30.6s , 70=2730 in direct locked up.
Whereas the 33 with 3.81s will do 70@2717 in Direct locked-up
By the math.

So lets start the want-list;
>must burn cheap gas
>Must get great fuel mileage
>Must have 3.81s or better rear gears. or somehow be at least as peppy as the hi-top.
> top cruising speed of say 75mph
>must be quiet in the cab
> no to the 2-speed rear axle
> yes to the A518 w loc-up
> 214/224 Comp roller, I need to know the rest of this story, advertised and LSA. I went to the Comp site but there is no navigating that new screw-up at least not for me.
> budget, budget, budget
operating elevation of about 1000 ft

So far it's kindof looking like a no-brainer to be the 408 bottom end. You already have all/most of the parts, and the A518 is a bolt-on. And you have a great selection of heads. The compression ratio of that combo is pretty easy to dial in. But that cam is pointing me in the wrong direction. Knowing a bit about Comps strategy, Ima guessing that is a 268/276/112+4 cam, which is a great power maker in a streeter.But if I'm right about the advertised specs, then the long exhaust duration steals power extraction and makes it a bit of a gas-hog, and there is nothing much you can do about it. In at 108, the power-extraction is only 106*. At that number, a lot of the energy in the expanding gasses is gonna go out the tailpipe. And because of that, the headers are gonna tug real hard on the intake during overlap, pulling mixture straight across the piston, and sending it out the pipes, not what you want. So lemmee know if I'm right or wrong about the Comp's advertised specs.
If it was my engine, for this combo, I would install a solid roller, because they have about the fastest flanks going, and I can get the advertised I need without sacrificing the power you want.
Then I can adjust the Scr to get the pressure I plan to run with at least something in your parts arsenal.
Here's my thinking; With a solid, suppose you could get an after-lash spec of 262/266/110+1 Your compression degrees would be 123 and the Ica would be ~57*. But here's the good news, your power extraction jumps to 116* with 44* of effective overlap.
But since it's a solid lifter cam, the .050 could be as high as 223/227 that's a great big winner right there. Don't care about the lift, this is not a race car.
Now, with 44* of Effective overlap, this engine will want a minimum cruising rpm of about 2200. That's a triple win! Now comes the hard part, getting the pressure down to stay out of detonation.
For iron heads
The Wallace likes 9.5 for 160psi@1000 ft and Ica of 57*. This is about perfect for IRON heads and midgrade gas at WOT with a tight-Q. The VP is predicted to be 162, which is spot on to get 6000pounds rolling with the crappy rear cruiser gear, that it's gonna take to cruise at 2200, with 33s; I get 3.08s for direct, 4.47s for overdrive. Hey that ain't so bad!

Ok but with alloy heads, you can jump the Scr up to 10.5 for pressure of 182, and I burn 87E10 right there, but the exciting part is that the VP has risen to an incredible 184. to This is gonna take a special induction system, and timing management, to soften the low-rpm hit so you can actually drive the thing. But running steady-state at 70 =2200 with 4.47 gears and 33" tires, with a VP of 184, the throttle will be barely open. Couple that with the 116* of power extraction, and modest 44* of overlap, I see a real fuel sipper.
And the best news of all; is that the cam is still a 223/227/110 @.050 so when you drop it into Second, at 55mph=3630/zero-slip, say 4200@15%slip, to pass some old granny, and the Rpm starts marching uphill, she will hit 5500 with ease doing 75mph @10% slip, still in Second gear,lol. Now, into overdrive and loc-up; 75 =2360, well past the minimum 2200.
I Like it.
So remember, that VP of 184 is gonna take some specialty work, in first gear, to not give your wife whiplash, every time your ankle bobbles. So now, lets soften the hit with stall;
Your starter gear is 2.45 x4.47 x 26.5/33=8.81 as compared to a 26.5" tire. That is an excellent number.
Lets say your stall is 2200, and this 408 has the potential to make 400 ftlbs there. At zero mph she has the WOT potential to plant
400 x8.81 x1.8TC multiplier =6340 footpounds, which I normalized to a 26.5" tire, so I can understand this. This might as well be a million ftlbs , because it is so huge. For normal take off, you might need 2500 to 3000, so your engine has like double of what you need , to burn rubber, if it was in a 3600pound Barracuda.
Now as soon as this rig begins to move, the multiplier in the TC will begin it's steady march towards it's minimum. Lets say in first gear from start to end, the multiplier averages 1.3. And lets say the 408 averages 440 ftlbs at WOT, over the useable rpm band, the new math is
440 x2.45 x4.47 x1.3=6264, and normalized to a 26.5 tire is 5030. This is really hard for me to fathom. Obviously, the 408 is only gonna need about 3000 of those at the best of times so, say 60% throttle (just guessing).
Ok let's get into second, with the Rs now at 3000rpm, and lets say the 408 is down to 415 ftlbs, then
415 x1.45 x4.47 x1.2 multiplier x26.5/33=2600ftlbs.. This is now coming into line with what the chassis needs , and as the rpm rises, power is still increasing, perfect.
Ok 5000 in second will be 63 mph, and into third the Rs will drop to 3450, so you have plenty of part Throttle torque there to climb the last 7 mph, easy peasy.
In fact, you have a preponderance of low-rpm torque in this scenario And I cannot help but wonder how you will be able to affect smooth power delivery with a single throttle body .
Ima thinking the 2000/2200 factory stall TC is out. Ima thinking you need a lil mushiness down there, say a 2600TC, so you can accelerate on the non-locked up part. If you get to 3200TC then VP don't count for nothing any more until everything gets locked up again at cruise rpm. Well hang on, is that bad? Not if you have a loc-up TC.
Another method is to retard the timing in first gear. And another is to run two or more staged throttle bodies. And another is to engineer an inverse proportional throttle activation mechanism, that opens the throttle very slowly in the first half of pedal travel, where you will be doing most of your accelerating, and then it speeds up to synchronicity at WOT. Yeah I like that last one . Now of course with a 2800TC you will need the lock up available at any time from second gear on, for fuel savings . With electric shift, that is no problem. There are several ways to engineer that.
For the coolest of cool, how about a gutted Thermoquad as a throttle-body, or any spread bore really, and a soft throttle stop for those testy take-offs. Hmmmm so many problems, lol, with too much VP. 184 is huge with a stroker.
My 367 has had a best of ~172, and I thought that was crazy.This 172VP netted tirespin at 50 plus mph, in 6.82 roadgear with 26.5 tires, from just a footstomp. And no help from a TC cuz mine is a manual trans.
184 is HUGE.
I would try it if I was you, cuz if it really is too much, you have enough parts to back up the bus.

However; recall that the iron numbers were pretty good as well with 162VP predicted at 9.5 scr@1000ft elevation. 162 and Iron is exceptionally good. If you ran that with a higher stall TC, to kill the effects of VP at take-off, and a loc-up to recover it at cruising, that would bring the iron heads into their own. Hmmmmm, decisions decisions.
I tell you what; how about backing off the Scr a bit with alloys say 10/1 Scr
Yeah, that will do it. Pressure predicted to be 171psi, down in the kerosene range for alloys, and VP predicted to run 173. Hey, that's a pretty good compromise! You can run any old stall-speed with that and tuning will be much easier. I like it. Well duh, I already ran 172,lol.

Ok this entire study is done on a solid-lifter cam with an Ica of 57degrees. With the new lower Scr numbers, you could easily put that on a hydraulic, and give up say 20 hp at 5000. Yur only gonna need those 20 once in a long long time .
Jus saying

Ok so to recap;
408 with alloy heads running 10.0 Scr and an Ica of 57 degrees to generate 173 psi at 1000 ft elevation.
My picks;
>You will need a timing computer.
>Headers yes, to make some power at higher rpms.
>You won't need the Keg; run it if you want to, but I'd leave on the shelf.
>If going EFI; run a single plain with a gutted big 4bbl.
>If carby'd; I'd stick a spreadbore hi-rise dual-plane on it with a spreadbore. >Fresh cold air absolutely yes.
>Run a minimum coolant temp of 180 to start but creeping up to 200 over time as you learn to trust your 7-blade mechanical fan on a thermostatic clutch.
>Run a stand alone trans cooler, to make it easy on your cooling system.
>Because of the length of your chassis, run the biggest pipes you can fit from headers to mufflers and at least 2.25s after that. Run long free-flowing 3 pass mufflers, 3 in/3 out and swedged down after the muffs. The big pipes have the advantage of running cooler, so the gasses condense and occupy less space, making it easier for the headers to do their magic. That's AJs Opinion. I hang mine down into the wind. But, then again, with the solid cam offering 116* of power extraction, a good dozen more than usual, your exhaust gasses may already be cool, relatively speaking. Yeah ok, run anything with the cam as described. But if you go to a wider LSA hydro, well you might want to come back to this ..
>I would run the loc-up on a relay triggered by a momentary-on sw, and grounded at a hobbs Vacuum sw to kick it out as the vacuum drops.
>The trans is gonna have to be beefed up a lil to put up with the abuse you are gonna dish out when you see how good this combo runs.
>You need to inspect your chassis. I suspect it is nothing more than a lightweight ladder-frame, and if/when you start pounding torque into it, it better not twist up and shred your fiberglass,lol. I'm no chassis guy so yur on your own there. Ima thinking outriggers,lol.
>Make sure your windows are secured, cuz when that 408 starts flexing, it might not be the only thing doing the flexing,lol.
Ok I'm just getting silly, I must be hungry,

Ok here is the last addition; I'm speaking from as you said; " What would AJ do". I invite anyone in who cares to shred me, cuz I wouldn't want to spend your money in the wrong places. Com'on boys , letRrip.

 

[mbaird]

I was wondering the weight as well .
Are those aluminum ?

 

[AJ/FormS]

I think OP said fiberglass skin.

 

[fishmens67]

Did you ever buy Jim a cup of coffee and a donut. lol

 

[mgoblue9798]

Well you sly dog you! What a great parts store house!
Do you have any clue as to the actual scale weight of the Travco?, not GVW
Do you know what rear gears are currently in it?
What does your hi-top scale at?, the one with the peppy 5.9. And what gears are in it?

I cannot speak to BigBlocks, never having had one.

Hit refresh as I'm adding as I go, cuz my computer has a tendency to freeze, and when it does, I loose the drafts.

OOPs. I see

So let's correct that to 33s and I get the 3.55s =3.29s, which represents a loss of performance of 7.3%, so the Travco, to remain on par with the same engine, would need 3.55s plus 7.3% = 3.81s
and the proof is;
with 3.55s and 30.6s , 70=2730 in direct locked up.
Whereas the 33 with 3.81s will do 70@2717 in Direct locked-up
By the math.

So lets start the want-list;
>must burn cheap gas
>Must get great fuel mileage
>Must have 3.81s or better rear gears. or somehow be at least as peppy as the hi-top.
> top cruising speed of say 75mph
>must be quiet in the cab
> no to the 2-speed rear axle
> yes to the A518 w loc-up
> 214/224 Comp roller, I need to know the rest of this story, advertised and LSA. I went to the Comp site but there is no navigating that new screw-up at least not for me.
> budget, budget, budget
operating elevation of about 1000 ft

So far it's kindof looking like a no-brainer to be the 408 bottom end. You already have all/most of the parts, and the A518 is a bolt-on. And you have a great selection of heads. The compression ratio of that combo is pretty easy to dial in. But that cam is pointing me in the wrong direction. Knowing a bit about Comps strategy, Ima guessing that is a 268/276/112+4 cam, which is a great power maker in a streeter.But if I'm right about the advertised specs, then the long exhaust duration steals power extraction and makes it a bit of a gas-hog, and there is nothing much you can do about it. In at 108, the power-extraction is only 106*. At that number, a lot of the energy in the expanding gasses is gonna go out the tailpipe. And because of that, the headers are gonna tug real hard on the intake during overlap, pulling mixture straight across the piston, and sending it out the pipes, not what you want. So lemmee know if I'm right or wrong about the Comp's advertised specs.
If it was my engine, for this combo, I would install a solid roller, because they have about the fastest flanks going, and I can get the advertised I need without sacrificing the power you want.
Then I can adjust the Scr to get the pressure I plan to run with at least something in your parts arsenal.
Here's my thinking; With a solid, suppose you could get an after-lash spec of 262/266/110+1 Your compression degrees would be 123 and the Ica would be ~57*. But here's the good news, your power extraction jumps to 116* with 44* of effective overlap.
But since it's a solid lifter cam, the .050 could be as high as 223/227 that's a great big winner right there. Don't care about the lift, this is not a race car.
Now, with 44* of Effective overlap, this engine will want a minimum cruising rpm of about 2200. That's a triple win! Now comes the hard part, getting the pressure down to stay out of detonation.
For iron heads
The Wallace likes 9.5 for 160psi@1000 ft and Ica of 57*. This is about perfect for IRON heads and midgrade gas at WOT with a tight-Q. The VP is predicted to be 162, which is spot on to get 6000pounds rolling with the crappy rear cruiser gear, that it's gonna take to cruise at 2200, with 33s; I get 3.08s for direct, 4.47s for overdrive. Hey that ain't so bad!

Ok but with alloy heads, you can jump the Scr up to 10.5 for pressure of 182, and I burn 87E10 right there, but the exciting part is that the VP has risen to an incredible 184. to This is gonna take a special induction system, and timing management, to soften the low-rpm hit so you can actually drive the thing. But running steady-state at 70 =2200 with 4.47 gears and 33" tires, with a VP of 184, the throttle will be barely open. Couple that with the 116* of power extraction, and modest 44* of overlap, I see a real fuel sipper.
And the best news of all; is that the cam is still a 223/227/110 @.050 so when you drop it into Second, at 55mph=3630/zero-slip, say 4200@15%slip, to pass some old granny, and the Rpm starts marching uphill, she will hit 5500 with ease doing 75mph @10% slip, still in Second gear,lol. Now, into overdrive and loc-up; 75 =2360, well past the minimum 2200.
I Like it.
So remember, that VP of 184 is gonna take some specialty work, in first gear, to not give your wife whiplash, every time your ankle bobbles. So now, lets soften the hit with stall;
Your starter gear is 2.45 x4.47 x 26.5/33=8.81 as compared to a 26.5" tire. That is an excellent number.
Lets say your stall is 2200, and this 408 has the potential to make 400 ftlbs there. At zero mph she has the WOT potential to plant
400 x8.81 x1.8TC multiplier =6340 footpounds, which I normalized to a 26.5" tire, so I can understand this. This might as well be a million ftlbs , because it is so huge. For normal take off, you might need 2500 to 3000, so your engine has like double of what you need , to burn rubber, if it was in a 3600pound Barracuda.
Now as soon as this rig begins to move, the multiplier in the TC will begin it's steady march towards it's minimum. Lets say in first gear from start to end, the multiplier averages 1.3. And lets say the 408 averages 440 ftlbs at WOT, over the useable rpm band, the new math is
440 x2.45 x4.47 x1.3=6264, and normalized to a 26.5 tire is 5030. This is really hard for me to fathom. Obviously, the 408 is only gonna need about 3000 of those at the best of times so, say 60% throttle (just guessing).
Ok let's get into second, with the Rs now at 3000rpm, and lets say the 408 is down to 415 ftlbs, then
415 x1.45 x4.47 x1.2 multiplier x26.5/33=2600ftlbs.. This is now coming into line with what the chassis needs , and as the rpm rises, power is still increasing, perfect.
Ok 5000 in second will be 63 mph, and into third the Rs will drop to 3450, so you have plenty of part Throttle torque there to climb the last 7 mph, easy peasy.
In fact, you have a preponderance of low-rpm torque in this scenario And I cannot help but wonder how you will be able to affect smooth power delivery with a single throttle body .
Ima thinking the 2000/2200 factory stall TC is out. Ima thinking you need a lil mushiness down there, say a 2600TC, so you can accelerate on the non-locked up part. If you get to 3200TC then VP don't count for nothing any more until everything gets locked up again at cruise rpm. Well hang on, is that bad? Not if you have a loc-up TC.
Another method is to retard the timing in first gear. And another is to run two or more staged throttle bodies. And another is to engineer an inverse proportional throttle activation mechanism, that opens the throttle very slowly in the first half of pedal travel, where you will be doing most of your accelerating, and then it speeds up to synchronicity at WOT. Yeah I like that last one . Now of course with a 2800TC you will need the lock up available at any time from second gear on, for fuel savings . With electric shift, that is no problem. There are several ways to engineer that.
For the coolest of cool, how about a gutted Thermoquad as a throttle-body, or any spread bore really, and a soft throttle stop for those testy take-offs. Hmmmm so many problems, lol, with too much VP. 184 is huge with a stroker.
My 367 has had a best of ~172, and I thought that was crazy.This 172VP netted tirespin at 50 plus mph, in 6.82 roadgear with 26.5 tires, from just a footstomp. And no help from a TC cuz mine is a manual trans.
184 is HUGE.
I would try it if I was you, cuz if it really is too much, you have enough parts to back up the bus.

However; recall that the iron numbers were pretty good as well with 162VP predicted at 9.5 scr@1000ft elevation. 162 and Iron is exceptionally good. If you ran that with a higher stall TC, to kill the effects of VP at take-off, and a loc-up to recover it at cruising, that would bring the iron heads into their own. Hmmmmm, decisions decisions.
I tell you what; how about backing off the Scr a bit with alloys say 10/1 Scr
Yeah, that will do it. Pressure predicted to be 171psi, down in the kerosene range for alloys, and VP predicted to run 173. Hey, that's a pretty good compromise! You can run any old stall-speed with that and tuning will be much easier. I like it. Well duh, I already ran 172,lol.

Ok this entire study is done on a solid-lifter cam with an Ica of 57degrees. With the new lower Scr numbers, you could easily put that on a hydraulic, and give up say 20 hp at 5000. Yur only gonna need those 20 once in a long long time .
Jus saying

Ok so to recap;
408 with alloy heads running 10.0 Scr and an Ica of 57 degrees to generate 173 psi at 1000 ft elevation.
My picks;
>You will need a timing computer.
>Headers yes, to make some power at higher rpms.
>You won't need the Keg; run it if you want to, but I'd leave on the shelf.
>If going EFI; run a single plain with a gutted big 4bbl.
>If carby'd; I'd stick a spreadbore hi-rise dual-plane on it with a spreadbore. >Fresh cold air absolutely yes.
>Run a minimum coolant temp of 180 to start but creeping up to 200 over time as you learn to trust your 7-blade mechanical fan on a thermostatic clutch.
>Run a stand alone trans cooler, to make it easy on your cooling system.
>Because of the length of your chassis, run the biggest pipes you can fit from headers to mufflers and at least 2.25s after that. Run long free-flowing 3 pass mufflers, 3 in/3 out and swedged down after the muffs. The big pipes have the advantage of running cooler, so the gasses condense and occupy less space, making it easier for the headers to do their magic. That's AJs Opinion. I hang mine down into the wind. But, then again, with the solid cam offering 116* of power extraction, a good dozen more than usual, your exhaust gasses may already be cool, relatively speaking. Yeah ok, run anything with the cam as described. But if you go to a wider LSA hydro, well you might want to come back to this ..
>I would run the loc-up on a relay triggered by a momentary-on sw, and grounded at a hobbs Vacuum sw to kick it out as the vacuum drops.
>The trans is gonna have to be beefed up a lil to put up with the abuse you are gonna dish out when you see how good this combo runs.
>You need to inspect your chassis. I suspect it is nothing more than a lightweight ladder-frame, and if/when you start pounding torque into it, it better not twist up and shred your fiberglass,lol. I'm no chassis guy so yur on your own there. Ima thinking outriggers,lol.
>Make sure your windows are secured, cuz when that 408 starts flexing, it might not be the only thing doing the flexing,lol.
Ok I'm just getting silly, I must be hungry,

Ok here is the last addition; I'm speaking from as you said; " What would AJ do". I invite anyone in who cares to shred me, cuz I wouldn't want to spend your money in the wrong places. Com'on boys , letRrip.

Answers to your questions.

270 Travco is built on M500 dodge chassis. Same as used in their medium to heavy duty trucks in the same period. It is not a lightweight deal at all and is overbuilt at least by motorhome standards. Just like Chrysler always liked to do. Its one reason why I love mopars.

Unit weight is about 12,000 lbs. Of course this can vary with fluid tank levels, add ons, etc. I will be pulling an additional 5k or so for the majority of the miles driven. This chassis has dual hydroboost brake systems with 15X 4in shoes on the back drums, and front discs. Braking should not be an issue as either the trailer or towed vehicle will have active brakes as well.

Cam specs are as follows, this is all the info I have on the custom grind at this point, it was taken in on trade on one of the 408 motors I took in as a core.

numbers/ letters are CC I 8705-06
lobes 3190s / 3314s
Hydraulic roller 108 +4
Xtreme Energy lobes:
266/276@.006
214/224@.050
141/145@.200
.353/.335 lobe lift

Another point, mentioned the 7 blade fan, it will be electric fans. Probably some from a dodge intrepid. those twin fans move 5000 cfm with both on high. They have worked great in both my dakota and van. Van especially as they are known for being hard to cool with the cramped engine comp. I am able to run 180 all day even during the summer months. Also free horsepower.

On the torque converter I wonder about the effect of stall speed and engine braking coming down grades.

 

[AJ/FormS]

numbers/ letters are CC I 8705-06
lobes 3190s / 3314s
Hydraulic roller 108 +4
Xtreme Energy lobes:
266/276@.006
214/224@.050
141/145@.200
.353/.335 lobe lift

Missed by 2 degrees.
That is a nice street cam for a 3500 pound car. Actually a very nice street cam. And it could be nice in your 17000 pound rig with hi-compression.
But I would install it at +2 instead of +4, because firstly, you won't need the extra 2* of compression. but you could use them over on the power-extraction side.Thus in at 106, the compression becomes 121 with an Ica of 59* and extraction becomes 112*, so she should be a tad better on fuel, over the long haul.
But the thing about that cam is the 55degrees of overlap That is a power maker at high rpm. but when cruising at low-rpm there is plenty of time on the exhaust stroke for the exiting tuned exhaust, to pull fresh fuel charge straight across the piston and out the back door, before the intake valve finally closes. As the rpm rises, there is less and less time for this to occur, but the vacuum effect of the headers also becomes stronger. So there is no good way that I can see to soften this thing. 55* is a lot of overlap for your purpose.
And then I guess we should mention the 59* Ica. By itself, in a streeter, this is a great number. What it means I'll guess you know, but I'll say it anyway; It means that your piston will be 59* past the bottom, when the intake reaches .006 tappet rise/ .0096 valve lift with 1.6 arms. still not quite closed. Your effective stroke at this point with a 4" arm is down to 3.27inches, so the pressure is dropping. It could be several to many more degrees before the valve actually seals and compression can begin.
That's not a totally a bad thing cuz once you wind her up a lil, the engine will begin to trap more and more mixture, and so power production begins.
But at low rpm, the piston will, during those 59 degrees and .730stroke, be pushing some of the just inducted fresh fuel charge, back up into the intake. And that is kindof bad for fuel-economy, if you happen to be cruising at a low-enough rpm.
IDK what your minimum cruise rpm will be for fuel economy, with this cam; I can't tell you until you get it running, then it is easy to figure out. But I can guess... based on the fact that I ran a Hughes cam of nearly the same spec. Mine had 53* of overlap at .008 tappet, which at .006 would probably be a lil more than 55. And my Ica was 64*, so about one size bigger than that Comp. It did pretty well at 2100, better at 2250 , but that was because, I think, I could get the timing closer at 2250. That's always the big key. My cranking pressure was about 185 or more, with 367 cubic inches.
So to cruise that cam at 2400, is probably gonna be on the cusp of fuel efficiency.
Also worth mentioning I suppose is that the 108LSA is pretty tight for this application. It will make a lil more power than a 112 or bigger, but it comes at the expense of powerband. You will probably feel the hole on the 1-2 shift which in the A727/518 is a 59%split. so if you shortshift at 4000, the Rs will drop to 4000 x.59=2360, which is well off the powerband, and even the high cylinder pressure, in the case of 17000 pounds, is not gonna like that, so the rig will tend to lose momentum going into Second. Rear gears will not cure this, the hole will always be there. So don't shortshift first!.
That cam will power peak around 5000, and with good heads, you can likely stretch it out another 400 in First so say 5400. Then, .59 x5400=3200, that will be at the very bottom of useful power. Thank goodness your rig will only be doing 39mph at this point with 4.56s out back, so Second gear has a chance to get back up on the cam which will probably begin around 3500/40 mph
The 2-3 shift is much tighter (.69) and won't be a problem.
Because of that 108LSa, I'm thinking the best of the powerband is gonna be from 1200 prior to the powerpeak to 400 after, so say 3800 to 5400; best guess.
3800 in Second will be 49 with 4.56s. So once you get there, then yur all set; top of second will get you very close to 70 with 4.56s . Then, The shift into drive, will get you .69 so 3730, right on the bottom of the powerband. But you don't care because you have reached your cruising speed. OD will then get you 2240 locked up, with those 4.56s.

By the way 1
All these numbers are for low-ET, maximum acceleration. If you ain't in a hurry, then you just don't wring out all the way, lol.

Btw-2
Just so you know, the 1-2 powerband requirement of the 727/518 is 1-.59=41% so at a shift of 5000, the requirement is 5000 x .41= 2050rpm. This means your engine's powerband should be at least about that.
Outshifting at 5400, the Powerband requirement is 5400 x .41=2200.
The selected 108cam, cannot get there, so it will always have a small hole. I'll guess 1600 shifting at 5400.
However, it makes up for it when you have to pass a slowpoke.
Say you had 4.56s and got stuck at 55mph. Downshifting into Second, will get you ~4450, and yur all set to pull out, and now that 108LSA will have a lil powerbulge on it beginning right about there, to slingshot your 408 to the moon. So while the 108LSA might be a tad narrow, for the 727 powerband requirement, it does have this going for it.
The 2-3 requirement is 1-.69=.31 so outshifting at 5400, the PB requirement is 1670, right on target for a 108LSa so no problem there.
The whole thing is just on the 1-2 shift.

Ok so how far off track did I get this time?

 

[AJ/FormS]

On the torque converter I wonder about the effect of stall speed and engine braking coming down grades.

Yeah I can't answer that; 17000 pounds is a pretty heavy deal.
If the sprag piles up; yur walking, so I guess the scuttlebutt would be to get an extreme duty,lol.
Early on I was thinking like 6000 pounds. Then when you said 12000 plus 5000, my jaw about hit the floor.
But Hey,good news, Travco thought the 318 was big enough........ I expect they knew their clientele would be towing stuff with it.

 

[mgoblue9798]

Yeah I can't answer that; 17000 pounds is a pretty heavy deal.
If the sprag piles up; yur walking, so I guess the scuttlebutt would be to get an extreme duty,lol.
Early on I was thinking like 6000 pounds. Then when you said 12000 plus 5000, my jaw about hit the floor.
But Hey,good news, Travco thought the 318 was big enough........ I expect they knew their clientele would be towing stuff with it.

OK, I just got a deal on a divorced gear vendors unit. I'll couple that with the 518 od. I am going to go with the 5.9 stroker and modified beer barrel and keep the hughes edlebrock for my 340 build.
Now I have got to get the rig running and brought home to start getting particulars like tire size and rear gear ratio before pickng a cam.